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This invention relates to a tungsten carbide and polycrystalline diamond, densely finned, heat dissipating module adapted for direct attachment to an integrated circuit heat producing device. More particularly, this invention relates to a module that reduces the number, and increases the efficiency, of the thermal junctions between the IC device and a cooling fluid in an actively cooled thermal management system. This is achieved by using the stiffness and thermal properties of a micro finned tungsten carbide body integrally bonded to a polycrystalline diamond buffer element that has an interfacial surface suitable for intimate attachment directly to the IC device.
High-speed integrated circuits in modern and future electronic applications demand more efficient cooling of the heat producing IC devices. Numerous attempts have been made to meet this demand as evidenced by the hundreds of patents issued over the past 20 years in this field. Although thermal management systems have been adequate in past applications, IC manufacturers looking to the future have begun to design and build circuits that exceed the limits of current thermal solutions as heat densities exceed 200,000 W/m2, or greater than the heat density of the sun""s surface.
Those skilled in the art are referred to the following patents that present four general categories of proposed solutions to the growing need for an efficient thermal management system in IC applications.
U.S. Pat. No. 5,455,382, incorporated herein by this reference, teaches the use of thin parallel plates formed by means of a multi-wire saw as means for producing a fined heat sink. The thin plates increase the convective surface area of the heat sink thereby increasing the efficiency of the convection into the surrounding atmosphere.
U.S. Pat. No. 5,455,457, incorporated herein by this reference, teaches the use of a heat diffusing plate attached to the IC device by means of a pliable electrically insulating resin layer. The plate is intended to shorten the path of heat conduction between the heat source and the finned heat sink. A metal cap is also used over the package in order to seal out contaminants.
U.S. Pat. No. 57,860,785, incorporated herein by this reference, teaches the use of a composite material as a heat sink. The composite consists of a combination of diamond power and cemented carbide particles sintered together.
U.S. Pat. No. 5,791,045, incorporated herein by this reference, teaches the use of fins coated with diamond by the chemical vapor deposition method.
What is needed is a cooling module that is tough, has high thermal conductivity, has high density micro fins for efficient convection into a cooling fluid, and has coefficient of thermal expansion compatible with the IC device so that it can be intimately attached to the IC device. A cooling module composed of tungsten carbide and diamond meets this need.
This invention presents a cooling module comprising tungsten carbide high-density micro fins integrally bonded to a polycrystalline diamond buffer element. The buffer element portion of the module features an interfacial surface suitable for direct attachment to a high heat producing integrated circuit device, such as a packaged silicon or silicon carbide semiconductor element. The thin, high-density fins are capable of withstanding the dynamics associated with thermal cycling of the IC device and the pressures and flows of a convective cooling fluid in an actively cooled thermal management system. The combination of tungsten carbide and polycrystalline diamond by the high-temperature high-pressure sintering method produces a module having a coefficient of thermal expansion compatible with that of the silicon element. The diamond buffer may be provided with a smooth, flat metalized surface for direct bonding to the device. The use of the polycrystalline diamond adjacent the device insures that the integrity of the bond will not be compromised due to differences in linear expansion during thermal cycling. Intimately bonding of the thermal module directly to the device reduces the number of thermal junctions and results in a direct thermal path between the semiconductor element and the convective cooling fluid circulated across the micro fins. Moreover, direct bonding of the module to the heat-producing element increases the convective efficiency of the cooling fluid, thereby permitting the semiconductor element to run faster.